Terminal for electric heating units



Oct. 30, 1928. 1,689,850

c. B BACKER TERMINAL FOR ELECTRIC HEATING UNITS Filed July 30, 1927 INVENTOR ATTORNEY mg tagent.

Patented a. 30, 1928.

UNITED STATES PATENT OFFICE.

. i GHRIgIIAN BER-GE BACKER, 01 NEW YORK, N. Y.

TERMINAL FOIVELECTRIC HEATING UNITS.

I v a ncauonmea July so,

tubular heater that shall embody means 00- operating with the casing for preventing turning and longitudinal movement of an electric-insulating bushing constituting a part of the terminal structure.

Another object of myin yention is to pro- Vide a terminal structure for a tubular heater that shall embody means to ensure that no lon 'tudinal pull or stress on. the terminal lea shall be transmitted to the resistor. 7

A further object-of my invention is to provide a terminal structure for an elongated tubular heaterthat shall permit of fully assembling the terminal structure in the tubular heater before treating the assembly with a high-pressure and high-temperature oxidizy invention is particularly applicable to V V encased, tubular heaters comprising atubular 2 5 metalv casing, a helical resistor wire located "therein and held tightly by a mass of initially metallic magnesium hydroxide. The terminal structure-proper embodies a'bushing of electric insulating material having a coaxial opening extending partially therethrough and communicating with a plurality of angu- .larly extending openings extending through the other portion of the bushing. The outer portion of the bushing extending beyond the end of the tubular casing is made substantially square in lateral section to permit of z peripherally spaced portions of-the endof .the casing being bent downwardly against the flat surfaces. A doubly bent conductor 40 wireis'loepe d around a portion of the plug or bushingv extending through, certain of the angularly extending openings. and through then-coaxial o ning and is twist'edwith an extending-entail? the resistor wire to provide a terminal lead.

' In thedrawings, Figure 1 is-a view, in side elevation, of one form of tubular heater comprisingljhe device embodying my invention,

1927. Serial n 209,424. v

Fig 2 is an enlarged View in longitudinal section through an end portion thereof,

a Fig. 3 is a view ofthe device shown in Fig. 2 looking fromleft to right, i

,Fig. 4 is a View in lateral section the line IVIV of Fig. 2,

Fig. 5 is a plan View of a terminal insulating bushing looking in the direction of the arrows on line V'Y of Fig. 2, and

Fig. 6 is a view, in longitudinal section,

taken on through a bushing of electric-insulating ma- I terial embodying my invention taken on the lines TI -VI of Fig. 5.

The terminal structure embodying my inventionis particularly applicable to a tubu lar electricheater of the. type shown generally --in Fig. l, designated by 11, and embodying an outer metal casing l2, a helically wound resistor wire 13 located therein and held tightly by a mass. 14 of initially metallic magnesium hydroxide and oxide extending peripherally of the helix 13." i

The method of production of the mass 14 of magnesium hydroxide is more particularly disclosed and claimed in my Reissue Patent No. 16,340. Briefly, the method comprises the location of an open helix of resistor wire,

such as the helix 13, in a tubular casing such as the casing 12, an open helix of a ID368118- sium strip being located therebetween. pon subjection of the'assembled structure'to the action of high-pressure and high-tem eraturefso' steamer water for a predetermine length of time, the initially metallic magnesium-is changed into a crystalline mass of magnesium hydroxide or oxide, which mass has a much greater volume than that of the magnesium 8.5 helix or member. The mass 14 isa crystal lin mass of magnesium hydroxide or oxide which not only holds the helix of resistor Wkre tightly within the casing, but provides also a heat-conducting pathfof low thermal resistance between the wire and the tubular casing. v One of the requirements-of complete trans'- formation of the initially metallic magnesium to magnesium oxide is that the high-temperature I and high-pres'sure oxidizing agent shall have continuous free access toall portions of the tubular casing and more particularly to the initially metallic magnesium, in order that all of the metallic magnesium shall be changed to magnesium hydroxide.

A plug or bushing 15, of electric-insulating 'material, such as steatite, porcelain or other suitable material, has an inner portion of such shape in lateral section, as to fit closely within an end portion of the casing 12, a shoulder portion 16 being provided in the inner surface of the tube, if desired, in order to limit the inward movement of the plug 15.

The outer portion of the plug 15 is substantially square in lateral section, and may be provided with rounded corners.

The outer half length of the plug 15 is provided with an axial opening 17 which is in communication with a plurality of angularly extending openings 18, 19, 20 and 21 located within the inner half portion of the plug 15. The opening 17 is slightly larger than are the openings 18 to 21, inclusive. As shown in the drawing, the openings 18 to 21, inclusive, communicate with the inner end of the opening 17 and those portions of the plug at the Junction point are preferably rounded over as shown more particularly in Figs. 2 and 6.

One end of the resistor wire 13 may extend through the opening 20 and through the opening 17 and therebeyond a suflicient distance to provide part of a terminal lead for the device. A looped piece of resistor wire 22 is pushed through openings 18 and 19 and the opening 17, after which it is twisted with the end of the resistor 13 extending through the opening 20 and the main opening 17 to provide a substantially flexible terminal lead havin a current-carrying capacity larger than t at of the resistor wire itself, in order to ensure that the terminal structure will operate at a relatively low temperature.

The inner faces or surfaces of the plug located radially inwardly from the openings 18 to 21 may also be rounded so that the loop 22 may be twisted tightl as shown in Fig. 2 of the drawing, with t e outer end of the resistor wire 13. A structure of this kind precludes the transmission of any longitudinal pull on the terminal lead to the resistor helix 13 itself.

As hereinbefore noted, I providefour angularly extending openings in the inner half portion of the plug or bushing 15, and use only three of these to receive the looped wire 22 and the resistor wire 13. Thisleaves the opening 21 free and unobstructed, whereby the entrance of the high temperature and high pressure oxidizing fluid required for transforming the initially metallic magnesium into magnesium hydroxide, is freely permitted. It is thus possible to completely l assemble the terminal plug, and the looped wire thereon in the end of the casing and on the terminal structure or the heating unit after it has thus been treated.

It is obvious that, while I have shown four radially extending openings in the inner portion of the plug 15, I may use a larger number in accordance with the number of looped terminal lead Wires, which I may desire to use.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a terminal structure for a tubular heater comprising a tubular casing and a re sistor therein, in combination, a plug of electric-insulating material insertable into the end of said casing, said plug having a coaxial opening extending partially therethrough, a plurality of angularly extending openings extending through the other portion of the plug and intersecting with said coaxial opening, one end of the resistor being inserted through one of the angularly e'zo tending openings and the coaxial opening, and a pair of said angularly extending openings,'and a terminal lead looped through said coaxial opening and twisted with the end of the said resistor.

2. In a terminal structure for a-tubular heater comprising a metal casing and a resistor wire insulatedly mounted therein, in combination, a plug of electric-insulating material in the end of said casing having an opening therethro-ugh of Y-shape, and a terminal lead wire extending through said opening and looped around a portion of the plug and twisted with one end of the resistor wire.

3. In a terminal structure for a tubular heater comprising a metal casing and a re sistor wire insulatedly mounted within the casing, in combination a plug of electric insulating material in the end of the casing, projecting therefrom and having an opening of Y-shape extending longitudinally therethrough, and a doubled-over terminal lead located in and extending from said plug, looped around a portion thereof and twisted with an end of the resistor wire.

4:. In a terminal structure for tubular or sheathed electric-resistor heaters, in combination, a bushing of insulating material adapted to fit into the ends of the tube or sheath, said bushing being provided with a longitudinally extending opening through a plurality of spa'eed openings extending whereb v the bus in when the bushing has been posithrough the bushmg'at an angle to its longitudinal axis and intersecting said longitu nally extending opening, and a conductor looped through said spaced openings and adapted to be twisted around said resistor said resistor may be anchored to tioned in t e-end of the tube or sheath.

5. A support and insulating bushing for tubular or sheathed electric-resistor heaters to,which the resistor may be anchored and by meansof which the terminal of the resistor is insulated from the tube or sheath, said support and bushing comgrising a block of insulating material provi ed with a longitudinally extending opening and a. plurality of s aoed o enings beginning from one end of t e bushing and extending at an angle to CHRISTIAN BERGH HACKER. 

